add class to provide some limited testing options

[dirk-thomas]

Closes #127.

The added class provides some limited ability to use new-style launch file to write tests. This allowed to port the following tests in Robot Web Tools:

• GT-RAIL/async_web_server_cpp@b2546f5
• GT-RAIL/rosauth@47b5dfb

[wjwwood]

lgtm

Long term it would be nice to have something that works with/like ros2 launch, but that will require some more thought and this is a good improvement for now.

[dirk-thomas]

Long term it would be nice to have something that works with/like ros2 launch, but that will require some more thought and this is a good improvement for now.

Absolutely, there is much more work needed in this area e.g. allowing test processes to generate result file.

[nuclearsandwich]

This PR has raised linter errors turning all nightlies unstable over the weekend. I've opened #132 to resolve them.

[t0ny-peng]

Hi @dirk-thomas
I see you've started moving launch_testing towards the new launch framework and this provides limited function(the test passed if all tested processed has rc 0). It would be nice to have regex feature like the legacy launch_testing. Is there any time table of this?

Or if you guys are too busy on other stuff, do you accept PR?

[dirk-thomas]

We are not actively working on this part. PRs are always welcome.